Microsoft chief executive Steve Ballmer has warned users of Red Hat Linux that they will have to pay Microsoft for its intellectual property. "People who use Red Hat, at least with respect to our intellectual property, in a sense have an obligation to compensate us," Ballmer said last week at a company event in London discussing online services in the UK.

If you believe Wikipedia, Microsoft has all kinds of covenants not to sue, even with Sun.

The patent 'landscape', if you will, is a World War I style powderkeg. Either it's defused via legislation restricting software patents and overturning existing ones, or it'll eventually blow up. I don't think ANYONE wants to see that happen, because the only ones who win will be everyone outside the USA who don't have to obey US patent laws.